A vacuum coating system is here a system with which articles can be coated under vacuum conditions and especially under high vacuum conditions. These systems include, for example, cathode atomizing systems (sputter systems), vaporization systems or chemical gas phase deposition systems.
An optical element is in the following an object or article which has the function of absorbing, transmitting, reflecting, refracting or scattering an electromagnetic radiation such as visible light, UV-radiation or IR-radiation. These articles include especially: lenses, for example, spectacle lenses or contact lenses. Also included are: planar optics and rounded optics, prisms, spherical or aspherical lenses, peripherally-shaped spectacle lenses, elliptical lenses, et cetera. In the following, a non-optical element is here an article of daily use, for example, a work tool or a part thereof such as drill bits or equipment parts.
The phrase “turning over an article” is in the following an operation wherein the surface of the article, which faces toward the coating source, changes in contrast to a pure rotating operation wherein the surface changes with respect to its position to the coating source, however, the surface remains facing toward the coating source. After a turnover of 180°, the back side of the optical element faces toward the coating source.
In the following, the invention is described with respect to an example of an apparatus and a method for turning over ophthalmic plastic lenses. In lieu of ophthalmic plastic lenses, other articles can, however, be turned over with the aid of the apparatus of the invention or with the aid of the method of the invention.
Thin optical layers are applied to the lens surfaces for the anti-reflection coating thereof. The anti-reflection coatings are produced in a high vacuum system. For this purpose, conventional optically effective materials are vaporized in high vacuum from a vapor source or are sputtered from a sputter source and deposited on the lenses. The lenses lie in holding rings or are clamped in clamping rings with one side of the lens facing toward the vaporization source or sputter source. The rings (lens holders) are usually placed in the cutouts of the sheet metal carriers which are mounted above the vaporization source so as to assume the form of a spherical cap and are rotated about the axis of symmetry of the spherical cap by means of a rotation device. The sheet metal carriers form segments of the spherical cap or, in the case of only one sheet metal piece, this piece forms the spherical cap itself. With the use of clamp rings, the lens holders lie with the clamped-in lenses statically in the sheet metal carrier and, after coating of the first lens side, are manually turned over together with the lenses to coat the second lens side. This method is characterized by obtaining, in general, a high yield. Contributing to this fact is that the lenses, in general, run through the vacuum process without being subjected to contamination because of abraded particles from mechanically moving components in the vacuum chamber.
Automatic turnover apparatus for lens holders permit a turning over of the lenses without the vacuum chamber having to be ventilated for manually turning over the lenses after the coating of the first lens side and thereafter be again evacuated. In this way, depending upon the process and system type, the total process time for coating both lens sides is significantly shortened. The conventional turnover apparatus are, however, subjected to several disadvantages for coating processes in the vacuum such as additional surfaces within the vacuum, additional friction surfaces, additional space requirement in the vacuum chamber, additional cleaning efforts and additional system complexities.
Numerous mechanically operating turnover devices have been suggested for automatically turning over the lenses. For example, U.S. Pat. No. 5,026,469 discloses an apparatus for holding and turning over lenses, especially, spectacle lenses in a high vacuum vaporization system having a spring biased ring pair as a lens holder. The lens holder is supported in a spherical cap-shaped sheet metal carrier about a rotational axis to which a toothed wheel is fixedly connected and which terminates in a right-angled bent finger. The finger comes into contact on the sheet metal carrier and limits thereby the rotation possibility of the axis to approximately 180°. The rotational axis can be rotated via the mechanical action of a rake on the toothed wheel which rake is disposed above the sheet metal carrier. The lens holder including the lens is turned over. In order to avoid a repeated mechanical contact with each rotation of the spherical cap, the rake is mechanically moved for the turnover operation in addition to the individual lens holders.
A vacuum coating system is disclosed in U.S. Pat. No. 4,817,559 wherein the segments of the spherical cap are turned over. The lens holders attached therein tilt only slightly about their own rotational axis in order to obtain the best possible orientation of the particular lens side with reference to the vaporization source before and after turning over.
U.S. Pat. No. 3,396,696 discloses a turning over of a plurality of lens holders with the aid of a magnet. The lens holders are mounted on a rotatable carrier. When the carrier is at standstill, a shaft can be moved with the aid of the magnet which turns over the lens holder via correspondingly assigned gears.
In addition, many mechanical turnover devices are known which take up a large portion of the surface available for the vaporization in the vaporization system. The capacity reduction associated therewith stands in contrast to the advantage of the shortening of the total operation of the coating of both lens sides.